Start Digital Edge with USB 6008

[NickNZ]

Hi,
I have a USB 6008 and I would like to know if start digital edge works with it. I can't get Acq&Graph Voltage-Int Clk-Dig Start&Ref example to work even though it says it is supported by the USB6008 (I get Error -200077 Requested value is not a supported value for this property. - I cant set the trigger to a digital line either...). So I am confused - does the digital edge trigger work with the USB 6008 or not?

What I would like to do is trigger a read of the counter on a falling edge on P0.0. (Dev1/port0/line0)

However I get Error -200452 Specified property is not supported by the device or is not applicable to the task.

I am using DAQMx 7.5 (I switched the USB 6008 to use the DAQmx 7.5 driver rather than the base driver).

Thanks for your help in advance.
Nick

[Quantumbyte]

Hi Nick,
The 6008 and 6009 devices only have one counter, and that is what is used to implement triggers. Therefore you can not trigger off of a digital port. However, I'm uncertain as to which value you're trying to set that is causing the -200077 error. If you scroll down at the error message you should get an explanation as to which parameter wasn't accepted. If you got the error when trying to set the trigger, I'd suggest you make sure your trigger source is /Dev1/PFI0, assuming that the 6008 is Dev1. If that is not the problem please post again with the rest of the information of the -200077 error, or attach your vi.

I hope this resolves the issue. Greetings

Daniel Domene
Portable DAQ R&D

[Otis]

Hi Nick,

The USB-6008 only has 1 PFI line, which is configured as either a trigger line or as a counter line.  Basically what you have to do if you want a triggered Counter Input is you will have to make a Software Trigger.  The way you do that is have a digital read that is monitoring whatever digital line you want and when it sees the line's state change it will begin the Counter Task.

I hope that clears up why you are getting the error.

Regards,

[NickNZ]

Hi
Thanks for your help.

The error message I am getting is 
Error -200077 occurred at Property Node DAQmx Trigger (arg 1) in DAQmx Reference Trigger (Digital Edge).vi->Acq&Graph Voltage-Int Clk-Dig Ref.vi
Possible reason(s):

Requested value is not a supported value for this property.

Property: Ref.TrigType
You Have Requested: Digital Edge
You Can Select: None

Task Name: _unnamedTask<C>

I was just running the Examples in the Example finder (LabView 7.0 with DAQmx 7.5). I have configured the USB to use the DAQmx driver rather than the Base.

Anyway I have solved my problem. I wanted to measure the Speed of a motor. I have implemented a hardware solution as an experiment with a signal generator, but I am going to program a micro to take the RPM signal, and output a 10kHz signal for 1 revolution and nothing for the next revoution. It also toggles a digital input that the software polls for a falling edge, when it is not outputing the 10kHz signal. There is plenty of time for the computer to read the counter before the next revolution as the motor runs at less than 3000 RPM. Its accurate enough with a 10kHz pulse train and I can get a speed update quickly enough in my software to be able to use PID control on the load.

Regards
Nicholas